This invention relates generally to semiconductor structures and devices and to a method for their fabrication, and more specifically to semiconductor structures and devices and to the fabrication and use of semiconductor structures, devices, and integrated circuits that include an epitaxially grown, high dielectric constant oxide to reduce leakage current density.
Epitaxial growth of single crystal oxide thin films on silicon is of great interest in numerous device applications, such as, for example, ferroelectric devices, non-volatile high density memory devices and next-generation MOS devices. Also, in the preparation of these films, it is pivotal to establish an ordered transition layer or buffer layer on the silicon surface for the subsequent growth of the single crystal oxides, such as, for example, perovskites.
Some of these oxides, such as BaO and BaTiO3 were formed on silicon (100) using a BaSi2 (cubic) template by depositing one fourth monolayer of Ba on silicon (100) using molecular beam epitaxy at temperatures greater than 850xc2x0 C. See, e.g., R. McKee et al., Appl. Phys. Lett. 59(7), p. 782-784 (Aug. 12, 1991); R. McKee et al., Appl. Phys. Lett. 63(20), p. 2818-2820 (Nov. 15, 1993); R. McKee et al.,Mat. Res. Soc. Symp. Proc., Vol. 21, p. 131-135 (1991); U.S. Pat. No. 5,225,031, issued Jul. 6, 1993, entitled xe2x80x9cPROCESS FOR DEPOSITING AN OXIDE EPITAXIALLY ONTO A SILICON SUBSTRATE AND STRUCTURES PREPARED WITH THE PROCESSxe2x80x9d; and U.S. Pat. No. 5,482,003, issued Jan. 9, 1996, entitled xe2x80x9cPROCESS FOR DEPOSITING EPITAXIAL ALKALINE EARTH OXIDE ONTO A SUBSTRATE AND STRUCTURES PREPARED WITH THE PROCESS.xe2x80x9d A strontium silicide (SrSi2) interface model with a c(4xc3x972) structure was proposed. See, e.g., R. McKee et al., Phys. Rev. Lett. 81(14), 3014 (Oct. 5, 1998). Atomic level simulation of this proposed structure, however, indicates that it likely is not stable at elevated temperatures.
Growth of SrTiO3 on silicon (100) using an SrO buffer layer has been accomplished. See, e.g., T. Tambo et al.,Jpn. J. Appl. Phys., Vol. 37, p. 4454-4459 (1998). However, the SrO buffer layer was thick (100 xc3x85), thereby limiting application for transistor films, and crystallinity was not maintained throughout the growth.
Furthermore, SrTiO3 has been grown on silicon using thick oxide layers (60-120 xc3x85) of SrO or TiO. See, e.g., B. K. Moon et al., Jpn. J. Appl. Phys., Vol. 33, p. 1472-1477 (1994). These thick buffer layers, however, would limit the application for transistors.
In CMOS applications, these types of oxide layers are fabricated using molecular oxygen and are formed thin (i.e., less than 50 xc3x85). Accordingly, a result is leaky films in which high electrical leakage is experienced due to oxygen deficiencies or vacancies. Furthermore, these films require a post-growth anneal in oxygen to reduce leakage current density across the oxide layer.
Accordingly, a need exists for a method for fabricating a high dielectric constant oxide on a semiconductor structure having low leakage current density.
It is a purpose of the present invention to provide for a method of fabricating a high dielectric constant oxide on a semiconductor structure having low leakage current density.
It is a further purpose of the present invention to provide for a method of fabricating a high dielectric constant oxide on a semiconductor structure in which the gate dielectric leakage current density is near zero.
It is another purpose of the present invention to provide for a method of fabricating a high dielectric constant semiconductor device structure using a high dielectric constant oxide such as (A)y(TixM1-x)1-yO3, wherein A is an alkaline earth metal or a combination of alkaline earth metals and M is a metallic or semi-metallic element.